Wilbur Frye

No-Tillage Agriculture

The no-tillage cropping system, a combination of ancient and modern agricultural practices, has been rapidly increasing in use. By the year 2000, as much as 65 percent of the acreage of crops grown in the United States may be grown by the no-tillage practice. Soil erosion, the major source of pollutants in rural streams, is virtually eliminated when no-tillage agriculture is practiced. The no-tillage system reduces the energy input into corn and soybean production by 7 and 18 percent, respectively, when compared to the conventional tillage system of moldboard plowing followed by disking. In addition, crop yields are as high as or higher than those obtained with traditional tillage practices on large areas of agricultural land.

Changes in soil properties after 10 years continuous non-tilled and conventionally tilled corn

Soil properties were evaluated after 10 years of continuous non-tilled and conventionally tilled corn (Zea mays L.) production on a Maury silt loam (Typic Paleudalfs) soil, which had been in bluegrass (Poa pratensis L.) for 50 years. On limed and nonlimed plots soil samples from 0, 84, 168 and 336 kg/ha N treatments were taken in the 0–5, 5–15 and 15–30 cm layers for determination of organic C and N, soil pH, and exchangeable Al, Mn, Ca, Mg, K. Tillage treatments had no effect on soil bulk density in the 0–15 cm layer. In the 0–5 cm surface layer, organic C and N were approximately twice as high with no-tillage as with conventional tillage; N fertilizer induced a high level of both organic C and organic N. No-tillage decreased soil pH for unlimed plots as compared to conventional tillage, especially at high N-rates, which produced an increase in exchangeable Al and Mn and a decrease in exchangeable Ca down to the 30 cm depth. When lime was applied, the pH of the surface soil was slightly higher under no-tillage. On treatments receiving lime, exchangeable Al and Mn levels were very low with no significant difference in tillage systems. At low rates of N fertilization the 10-year average corn yield was higher for conventional tillage than for no-tillage, but at high rates of N fertilization it was equal or higher for no-tillage treatments receiving lime. Unlimed no-tillage treatments produced lower yields at all N levels during 1975–1979. Deterioration of soil physical properties was not observed.

Legume Winter Cover Crops

Throughout virtually all of the history of agriculture, the nitrogen harvested from cropped soils has been replenished, if it has been replenished at all, by leguminous nitrogen fixation. Although animal wastes, nonsymbiotic fixation, and atmospheric deposition can be significant sources of N, a large fraction of the first can be traced to legume sources and the latter two are generally insufficient to maintain productivity of cropland. In the Mediterranean Civilizations, documented recognition of the value of green manures can be found as early as the writings of Xenophon, who lived from 434 to 355 B.C. (according to Wedderbuan and Collingwood, 1976). Semple (1928), in a review of ancient agricultural practices, indicated that several writers have specifically discussed the use of legumes for soil improvement. Theophrastus (373–287 B.C.) wrote of bean crops being used as green manure by farmers of Macedonia and Thessaly. Cato (234–149 B.C.) and Columella (about 45 A.D.) compared the value of various legumes in soil improvement. Lupine was a favored legume for this purpose. According to Pieters (1927), Chinese writers recognized more than 2,000 years ago that legumes increased production of the crops that followed. As is often the case now, development of these practices by farmers may considerably predate their consideration by academics.

Fertilization and Liming

Fertilizing and liming crops grown under no-tillage is not radically changed when compared to conventional practices. There are differences, however. Most of these differences arise from the fact that, under no tillage, the soil is not moved nor disturbed except in the slot where the seeds are placed. Also, under most systems of no-tillage, a residue of dead plant material is left on the soil surface and a kind of natural mulch is formed. The non-disturbance of soil resembles conditions in permanent pasture so that principles proved there are valid for row crops grown under no-tillage in general. The presence of a surface mulch changes the soil water regime, particularly at the soil surface. Principles of fertilization and liming for no-tillage are based on these two conditions as well as on the nutrient requirements of plants and the specific soil and climatic conditions encountered.

Energy Requirement in No-Tillage

The production phase of U.S. agriculture uses large amounts of fossil energy as gasoline, diesel fuel, natural and L-P gas, oil, electricity, fertilizers, pesticides, feeds, seeds and machinery. Figure 6-1 shows an estimated division of the energy among the major uses in production agriculture. About one-third of the energy is directly from fossil fuels. Indirect inputs of fossil energy as fertilizers, pesticides, feeds, seeds machinery and electricity make up the remaining two-thirds. Of the fuels, gasoline comprises about 40 percent, diesel fuel 32 percent, natural gas 16 percent and L-P gas 12 percent (USDA-ERS-FEA, 1977). Most of the on-farm use of diesel fuel and gasoline is in farm tractors, trucks and automobiles, uses for which energy substitution is for the most part impractical. L-P gas is used mainly for on-farm crop drying. The major on-farm use of natural gas is for irrigation and for grain drying, especially in large commercial operations. Much of the indirect use of natural gas in agriculture is in the form of nitrogen fertilizer, since almost all nitrogen fertilizer used in the U.S. is manufactured from natural gas. An estimated 89 percent of the energy used in production agriculture goes for crop production and the remaining 11 percent is used for livestock production (Soil Conservation Society of America, 1978).

Sustaining Soil Quality with Legumes in No-Tillage Systems

Abstract Tillage, cropping system, and cover crops have seasonal and long‐term effects on the nitrogen (N) cycle and total soil organic carbon (C), which in turn affects soil quality. This study evaluated the effects of crop, cover crop, and tillage practices on inorganic N levels and total soil N, the timing of inorganic N release from hairy vetch and soybean, and the capacity for C sequestration. Cropping systems included continuous corn (Zea mays L.) and stalk residue, continuous corn and hairy vetch (Vicia villosa Roth), continuous soybeans (Glycine max L.) plus residue, and two corn/soybean rotations in corn alternate years with hairy vetch and ammonium nitrate (0, 85, and 170 kg N ha−1). Subplot treatments were moldboard plow and no tillage. Legumes coupled with no tillage reduced the N fertilizer requirement of corn, increased plant‐available N, and augmented total soil C and N stores.

Nitrogen availability from alfalfa suppressed or killed for no‐till production

Abstract There is interest in intercropping perennial legumes with com (Zea mays L.) under no‐tillage soil management. Evaluation of N availability by measuring plant N uptake in field research trials with such systems is often complicated by competition for water. We monitored soil inorganic N (ammonium and nitrate) levels at 14‐day intervals for 42 days at 0–10 cm and 10–20 cm soil depths after an alfalfa (Medicago sativa L.) sod was subjected to four different suppression treatments: a) cut and remove, b) cut and return, c) above‐ground kill with paraquat, and d) complete kill with glyphosate. The initial (14 day) release of N was similar in all treatments where residues were left or returned, but alfalfa regrowth immobilized much of the N mineralized in all treatments, except where alfalfa was killed. The greatest quantity of soil inorganic N was found on day 28 where alfalfa was killed, equal to nearly 72% of the N contained in the alfalfa topgrowth. Soil nitrate N concentrations, averaged to a depth...